1. Field of the Invention
The present invention is directed to an apparatus for winding filaments. More particularly, the present invention is directed to the perfect layer winding of coils of metal wire on bobbins.
2. Description of the Background Art
Machines for winding coils of filaments such as wires on bobbins are well known. Typically, these involve a rotating spindle upon which a bobbin is mounted. The end of a wire filament is fixed to the bobbin and wound thereupon during rotation of the spindle. The formation of discrete layers of perfectly wound wire requires that there be provided some sort of traverse mechanism for guiding the position of the wire along the axis of rotation of the bobbin during winding.
A common problem is that of precise coordination between the motion of the traverse mechanism and the axial point of winding on the bobbin. The axial position of the traverse mechanism should be slightly retarded with respect to the point of winding of the wire, in the winding direction, in order to assure that the turns of wire being wound on the bobbin are always preloaded against each other. This retardation of the position of the traverse produces an angle, called a "load angle", of the wire relative to the perpendicular to the rotational axis of the bobbin and spindle. In order to assure perfect winding, the load angle must be large enough that the turns are always preloaded against each other, but must be small enough to avoid crossovers of the turns onto the previously wound turns. The load angle may also be called the "wire guide angle."
Theoretically, if one knows the nominal diameter of the wire being wound and the rotational speed of the spindle, the advance speed of the traverse can be calculated to maintain a desired load angle Ad. However, in practice, variations in the wire diameter and bobbin length can cause the load angle to vary sufficiently that adjacent turns of the wound wire may have spaces between them, or there may be crossovers. Some sort of feedback system is therefore desirable for maintaining the load angle at the desired value "Ad".
Numerous feedback systems have been proposed. Typically, they involve adjusting the speed of the traverse mechanism so as to correspond to a desired speed providing a predetermined load angle. However, this made it impossible to wind more than one spool at a time since the speed of the traverse mechanism could not then conform to that necessary for plural, simultaneously wound bobbins.
U.S. Pat. No. 4,741,500 to Lavanchy discloses a process for winding cable in which a load angle controls a motor so as to maintain a correct winding position for the cable being wound. The motor could drive either the guide or the spool, however there is no disclosure of using the load angle of several cables guided by a single traverse mechanism or for separately adjusting the rotational speed of more than one spool.